1. Field of the Invention
The invention relates to an information signal recording apparatus for recording an information signal having a wide frequency band onto a recording medium.
2. Description of the Related Art
The luminance signal component of a TV signal has been prescribed to have a frequency band of about 4.2 MHz. Meanwhile, as a result of decrease in cost of semiconductor memories, it has recently come to be practiced to minimize a flicker and to increase vertical resolution by converting scanning lines in such a way as to change an interlaced picture plane into a non-interlaced picture plane.
However, although the vertical resolution can be increased by this, there arises an unbalanced state between the horizontal and vertical resolutions, because the band of 4.2 MHz which defines the horizontal resolution has not been determined relative to the vertical resolution obtained in the case of interlacing arrangement.
To eliminate this unbalance, efforts have become active to raise the frequency band up to 6 MHz or thereabout. These efforts include, for example, a movement for EDTV (extended definition television). In the case of EDTV, in order to retain interchangeability with the signals to be handled by the conventional transmission method, a transmission system is arranged, for example, to separate only a high frequency component which has frequencies, for example, from 4 to 6 MHz and to frequency interleave and multiplex transmit the component thus separated.
It is also being contemplated for a still picture recording/reproducing system, such as a still video system which requires a high degree of definition in particular, to record a high frequency component and a low frequency component separately on a recording medium.
FIG. 5 of the accompanying drawings is a circuit diagram showing the reproduction system of the above stated still video system. As shown, the conventional system has been arranged in general to reproduce the low frequency component and the high frequency component separately from each other and then to add them together before various signal processing operations.
The arrangement of FIG. 5 simplifies the circuit arrangement as it requires only a single signal processing circuit 22. On the other hand, however, the conventional system is disadvantageous for removing noises. According to this arrangement, the noise removal must be carried out by firstly removing the noise in the high frequency component and then removing the noise in the combined signal including the high frequency component and the low frequency component. Therefore, the conventional system either has complicated the signal processing operation or greatly degraded the resolution of the picture.
The still video systems have unified standards already established for them. In accordance with the standards, a still video system is allowed to record and reproduce a luminance signal of a frequency band up to 4.5 MHz. However, this value 4.5 MHz (more exactly stated, 4.2 MHz in the case of the NTSC color system) has been determined by the NTSC on the assumption of recording and reproduction of a motion picture. Hence, this value is not apposite to recording and reproduction of a still picture.
Further, as mentioned in the foregoing, the non-interlacing arrangement for TV receiver which has been prompted by the recent improvement in the performance of semiconductor memories has come to result in an increase in the vertical resolution which now presents a problem with respect to the unbalance of the horizontal resolution relative to the increased vertical resolution.